Biological behavior and natural course of acral malignant melanoma. Clinical and histologic features and prognosis of palmoplantar, subungual, and other acral malignant melanomas.

This study, based on 67 Japanese cases of acral malignant melanomas, presents their gross clinical and histologic features and the natural history of the lesions with respect to anatomic locations, thicknesses, and sex of patients afflicted. We found that the anatomic locations of malignant melanomas in Japanese are unique in the sense that more than 40% of cutaneous melanomas occurred in palmoplantar and subungual sites, about 80% showed the clinical and histologic features of the acral lentiginous type, 15% were in the form of nodular malignant melanoma, and 3% in the form of superficial spreading malignant melanoma. We did not find any difference in prognosis of acral malignant melanomas from that of malignant melanomas on other parts of the body. Neither was there significant difference in the overall survival rates or in the survival rates within same range of thickness. There was some difference in the survival rates of patients with palmoplantar and subungual malignant melanoma of men and women, the women being younger and having better survival rates than the men. However, no significant difference was found in survival rates from the factor of thickness of lesion. Our study indicates the usefulness of specifications of thickness and anatomic site in predicting biological behavior and natural course of acral malignant melanomas.